Well(s) containing filtration devices

ABSTRACT

A single or multiwell plate using membrane, preferably an ultrafiltration membrane to filter selected solutes from a liquid is disclosed. In particular, a preferred construction and method of sealing the membrane to the interior of the well so as to form an integral seal between the top portion of the well and the boftom portion is disclosed. The preferred method is to use a heat seal device which secures the filter to the underdrain portion of the device.

The present invention relates to a single or multi-well filtrationdevice suitable for the concentration or assay of biological andbiochemical materials. The present invention more particularly relatesto a single or multi-well filtration device having the filtration mediasealed to the underdrain of the device.

BACKGROUND OF THE INVENTION

Test plates having one or more individual wells or reaction chambers arecommon laboratory tools. Such devices are employed for a wide variety ofpurposes and assays, see U.S. Pat. No. 4,902,481. Single welled devicesare also well known, see U.S. Pat. Nos. 3,483,768, 4,632,761 and4,722,792.

The plate filtration devices include two plates, the upper plate,commonly referred to as the well plate and a lower plate, commonlyreferred to as the underdrain. The well plate contains one or moreindividual wells that are open at one end and have a filtration membranesealed across the opposite end. The underdrain is provided with a secondset of individual well(s), which register with the wells of the wellplate. Each of the wells in the underdrain have an open end and a secondend which contains a small opening having a spout which opening andspout are designed to receive liquid which passes through the filtrationmembrane of the upper plate. The size of the opening and the spout arecontrolled so that liquid is retained in the well plate above themembrane under normal atmospheric conditions due to surface tensionforces but passes through the membrane and the opening and spout when apressure differential is applied across the membrane.

The filtration media has been secured to the lower portion of the wellplate in several ways. In one method, a sheet of filtration membrane isstretch across the bottom of the well plate and adhered to each of theindividual well or wells. In a second method, individual membrane piecesare cut and placed within the interior of the well where either frictionor an undercut is used to maintain the position of the membrane in thewell. In a third common method, the individual pieces are adhered to thebottom portion of the individual wells of the well plate.

The first method has problems in that liquid that passes through themembrane can travel laterally between wells and contaminate adjacentwells. The second method relies upon proper placement and maintenance ofthat placement in the well over time. Vibration, rough handling andother factors can displace the membrane causing loss of the sample or atleast a portion of the sample or liquid within the sample. Additonally,it fails to form an integral seal such that liquid may bypass the filteraltogether resulting in loss of product and contamination of thefiltrate. The third method has been the preferred and most commonly usedmethod as it ensures that there is no cross talk or contaminationbetween the wells and there is a true seal of the membrane to the wellplate so as to prevent leakage.

In these devices, the membrane has been limited to microporous membraneor a glass fiber depth filter or other coarse filtration media. This isdue to the nature of the membrane and its ability to be sealed to thebottom of the well in the well plate. Other membranes, in particularultrafiltration (UF) membranes are mentioned as being of possible use,however they have not been successfully sealed within the well plate.This is due to the structure and composition of the UF membranes. Thesemembranes are relatively thin and fragile. Therefore these membranes aretypically cast upon a support structure such as a non-woven porous sheetor a microporous membrane. The UF membrane itself is a relatively thin,dense material which is extremely sensitive to any type of mechanical orchemical bonding method.

What is desired is a plate system which allows for the use of membranesother than microporous membranes and which contains all of theadvantages of the prior plates, namely avoiding lateral flow andcontamination between the wells and the use of multiple wells in thesame device. The present invention provides such a device.

SUMMARY OF THE INVENTION

The present invention provides an improved single or multi-wellfiltration apparatus that permits the use of membranes other thanmicroporous membranes, in particular UF membranes, nanofiltrationmembranes and reverse osmosis membranes. Additionally, the presentinvention provides such a device that is capable of having liquidremoved from each well by filtration with a vacuum or under pressureincluding by centrifugal forces. The filtrate from each well isrecovered separately from the filtrate in adjacent wells. Thus, thisapparatus permits the recovery and/or analysis of the retentate and/orfiltrate without cross contamination between the adjacent wells.

The present invention has a well plate having both ends open and anunderdrain that has one end (the lower end) essentially closed exceptfor a small opening and spout. The other end of the underdrain has afiltration membrane sealed across the well such that any liquid will beretained in the well of the well plate until either a vacuum or positivepressure is applied to filter the liquid through the membrane. Themembrane is sealed to the well of the underdrain by any conventionalmethod such as heat bonding, ultrasonic bonding, vibrational bonding,friction bonding, adhesive bonding, solvent bonding or overmolding. Itis preferred that the membrane be sealed to the underdrain by heatbonding.

It is a preferred object of the present invention to provide afiltration device having an underdrain portion having one or moreindividual drain compartments, each of said one or more compartmentshaving a drain opening and a drain compartment wall located adjacent theouter periphery of each compartment; one or more filter componentslocated in one or more of the drain compartments contained in theunderdrain portion, each of said filter components being attached to theunderdrain portion in a manner to form in integral seal between theperiphery of the filter component and a drain compartment of theunderdrain portion; and a well plate having one or more individualwells, said plurality of wells being arranged in number and location soas to register with the underdrain portion.

It is another preferred object of the present invention to provide amultiple well device having an underdrain portion having a plurality ofindividual drain compartments, each of said compartments having a drainopening formed in the lower portion of the compartment and a draincompartment wall located adjacent the outer periphery of thecompartment; a plurality of filter components contained in at least aportion of the compartments of the underdrain portion, each of saidfilter components being attached to the underdrain portion so as to forman integral seal between the periphery of the filter component and thecompartment of the underdrain portion; and a well plate having aplurality of individual wells, said plurality of wells being arranged ina number and location so as to register with the underdrain portion whensaid well plate is placed onto of the underdrain portion.

It is a further preferred object of the present invention to provide amethod of forming a multiple well filtration device by forming anunderdrain portion, said underdrain portion having a plurality ofindividual drain compartments, said compartments having a drain opening,a filter support surrounding said drain opening and a drain compartmentwall located adjacent the outer periphery of the filter support; placinga filter component in each of the drain compartments contained in theunderdrain portion, attaching the filter component in each of said draincompartments at the periphery of the filter component to the draincompartment in a manner to form in integral seal between the peripheryof the filter component and a drain compartment of the underdrainportion; forming a well plate having a plurality of individual wells,said plurality of wells being equal in number and location with thenumber and location of the plurality of drain compartments in theunderdrain portion; and securing the well plate to the underdrainportion so as to form a plurality of sealed well filtration devices,each having a well, a drain and a filter sealed in between.

It is a further preferred object of the present invention to provide afiltration apparatus formed of a first plate having at least one firstwell, each of said at least one first wells having a first open end anda second open end and an outside peripheral surface, a second platehaving at least one second well having a first open end, a first closedend, said closed end having a hole extending through the closed endthickness and an inside peripheral surface, said second plate beingsecured to said first plate so as to form a continuous well between thetop of the first plate and the first closed end of the second plate, afilter positioned between said second end of said first plate and saidfirst closed end of said second plate and an open spout having an openend, said spout being in fluid communication with said hole.

These and other embodiments and objects of the present invention will bemade clear from the following description and claims.

IN THE DRAWINGS

FIG. 1 shows a first embodiment of the present invention in crosssectional view.

FIG. 2 shows a second embodiment of the present invention in crosssectional View.

FIG. 3 shows a third embodiment of the present invention in crosssectional view.

FIG. 4 shows another embodiment of the present invention in crosssectional view.

FIG. 5 shows a further embodiment of the present invention in crosssectional view.

FIG. 6 shows an additional embodiment of the present invention in crosssectional view.

FIG. 7 shows a first method and device for sealing the membrane into thedevice of the present invention in cross sectional view.

FIG. 8 shows a first embodiment of the sealing device of the presentinvention in cross sectional view.

FIG. 9 shows an alternative embodiment of the sealing device of thepresent invention in cross sectional view.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 is shown a first embodiment of the present invention. In thisembodiment the device is formed of a single plate 1. This plate 1 hasone or more wells 2. In the embodiment as shown the one or more wellsrise up from a planar portion 3. Alternatively as shown in FIG. 2, thewells may depend downwardly from the planar portion 3. The inner wall 4of the one or more wells forms the wells themselves. The wells areclosed at the bottom 5. An opening 6 is formed in the bottom of thewells to as to form a fluid communication between the inner surface ofthe bottom 5 of the well and the exterior surface 7 of the bottom 5. Afilter 8 is contained in the well as shown in FIGS. 1 and 2 adjacent thebottom 5. The filter is sealed to the inner surface of the well so as toseparate the opening 6 from the rest of the well. This sets up a fluidtight seal between the two well portions such that all fluid that is topass through the opening 6 must first pass through the filter 8.

Referring to FIG. 3, a filtration device according to a secondembodiment of the invention is shown. The device shows a first plate 11having at least one well 12. The well 12 has an inner peripheral wall 13and an outer peripheral wall 14. The top and the bottom of the well, 15and 16, are open. The second plate 17 has at least one well 18 having afirst opened end 19 and a second closed end 20. The second closed end 20has an opening 21 that passes from the interior of the well 18 to theexterior of the well 22. The inner surface of the second closed end 20may have a filter support 23 which extends across a significant portionof the closed end 20 leaving a raised periphery 24 adjacent the innerwall 25 of the well 18 as shown in the Figure. Altematively, no filtersupport 23 may be used and the inner surface of the second closed endmay be substantially planar (not shown). Optionally as shown, the secondplate 17 may have a collar 26 which surrounds each opening 21 of eachwell 18 in order to prevent any fluid from one well from entering ormixing with the fluid of an adjacent well. A filter 27 is secured withinthe well 18 about its periphery to the raised periphery 24 of the closedend 20. In those embodiments which use no filter support or raisedperiphery, the filter is simply secured adjacent the bottom of theclosed end. The filter 27 is secured to the periphery 24, if used oradjacent the bottom of the closed end, if not used, such that it forms aliquid type seal between the filter 27 and the area of the bottom of theclosed end adjacent the opening of the well such that all liquid mustflow through the filter before entering the opening.

As shown, the first plate 11 is secured to the second plate 17. Theseplates 11 and 17 may be secured by a snap or press fit between the wellsof the two plates which allow the frictional forces between the innersurface of one well and the outer surface of the other well to hold thetwo plates together. As shown, the outer surface of the first plate wellis secured to the inner surface of the second plate well. Altematively,the outer surface of the second plate well may be secured to the innersurface of the first plate well. Additionally, rather than using a snapor press fit to form a removable secure fit between the plates, one mayuse a thermal bond or adhesive bond to permanently secure the two platestogether. In an additional embodiment of the present invention, thefirst and second plates are secured together by an overmolding orinjection molding process. The method by which the two plates aresecured is a matter of choice to the practitioner.

FIGS. 4 and 5 show an alternative filter arrangement for the embodimentof FIG. 3. In these embodiments, the filter 27 rather than being sealedadjacent the bottom of the well of the second plate is secured adjacentthe top 28 of the well of the second plate. In this embodiment it ispreferable, although not necessary that the well of the second plate beof a depth less than that of the first plate. When assembled the well isformed between the two plates and the filter is still sealed above theopening and still causes all liquid to flow through the filter beforeentering the opening.

These embodiments allow for simpler manufacturing as a sheet of filtermaterial may be laid across the upper surface of the second plate andsealed adjacent to the periphery of the inner well wall of the secondplate. Excess filter material is then removed leaving discrete isolatedfilters at each well of the second plate, which are incapable of anycrosstalk or contamination. Alternatively, one may still use individualfilter pieces and secure them to the area adjacent to the inner wall ofthe well of the second plate.

In a further embodiment (not shown) one may use more than one filter ina single well. Typically, these filters are arranged on top of eachother. Only the bottom most filter needs to be sealed in a fluid typearrangement with the compartment. Preferably all filters are sealed soas to ensure complete filtration. Altematively, some wells may containno filter element at all. One may also vary the filters used between thevarious wells so that one may obtain a series of different filterelements within the same multiple well device.

Suitable polymers which can be used to form the underdrain and if usedthe well plate include but are not limited to polycarbonates,polyesters, nylons, PTFE resins and other fluoropolymers, acrylic andmethacrylic resins and copolymers, polysulphones, polyethersulphones,polyarylsulphones, polystryenes, polyvinyl chlorides, chlorinatedpolyvinyl chlorides, ABS and its alloys and blends, polyolefins,preferably polyethylenes such as linear low density polyethylene, lowdensity polyethylene, high density polyethylene, and ultrahigh molecularweight polyethylene and copolymers thereof, polypropylene and copolymersthereof and metallocene generated polyolefins. Preferred polymers arepolyolefins, in particular polyethylenes and their coploymers,polystyrenes and polycarbonates. When an underdrain and well plate areused in combination they may be made of the same polymer or differentpolymers as desired. Likewise the polymers may be clear or renderedoptically opaque or light impermeable. When using opaque or lightimpermeable polymers, it is preferred that their use be limited to theside walls so that one may use optical scanners or readers on the bottomportion to read various characteristics of the retentate. When thefilter is heat bonded to the underdrain, it is preferred to usepolyolefins due to their relatively low melting point and ability toform a good seal between the device and the filter.

The filter may be of any variety commonly used in filtering biologicalspecimens including but not limited to microporous membranes,ultrafiltration membranes, nanofiltration membranes, or reverse osmosismembranes. Preferably microporous membranes, ultrafiltration membranesor nanofiltration membranes are used. Even more preferably,ultrafiltration membranes are used.

Representative suitable microporous membranes include nitrocellulose,cellulose acetate, polysulphones including polyethersulphone andpolyarylsulphones, polyvinylidene fluoride, polyolefins such asultrahigh molecular weight polyethylene, low density polyethylene andpolypropylene, nylon and other polyamides, PTFE, thermoplasticfluorinated polymers such as poly (TFE-co-PFAVE), polycarbonates orparticle filled membranes such as EMPORE® membranes available from 3M ofMinneapolis, Minn. Such membranes are well known in the art (addMillipore patent numbers) and are commercially available from a varietyof sources including Millipore Corporation of Bedford, Massachusetts. Ifdesired these membranes may have been treated to render themhydrophilic. Such techniques are well known and include but are notlimited to grafting, crosslinking or simply polymerizing hydrophilicmaterials or coatings to the surfaces of the membranes.

Representative ultrafiltration or nanofiltration membranes includepolysulphones, including polyethersulphone and polyarylsulphones,polyvinylidene fluoride, and cellulose. These membranes typicallyinclude a support layer that is generally formed of a highly porousstructure. Typical materials for these support layers include variousnon-woven materials such as spun bounded polyethylene or polypropylene,or glass or microporous materials formed of the same or differentpolymer as the membrane itself. Such membranes are well known in theart, and are commercially available from a variety of sources such asMillipore Corporation of Bedford, Massachusetts.

As described above, while one well in each plate can be used; it isenvisioned that a plurality of wells will be used. When a plurality ofwells are used, it is important that the wells of the first plateregister with the wells of the second plate. Typically multiple wellplates have been made in formats containing 6,96,384 or up to 1536 wellsand above. The number of wells used is not critical to the invention.This invention may be used with any multiple number of wells providedthat the filter is capable of being secured to the second plate in amanner which forms a liquid fight seal between the periphery of thefilter and the inner surface of the closed end of the wells of thesecond plate. The wells are typically arranged in mutually perpendicularrows. For example, a 96 well plate will have 8 rows of 12 wells. Each ofthe 8 rows is parallel and spaced apart from each other. Likewise, eachof the 12 wells in a row is spaced apart from each other and is inparallel with the wells in the adjacent rows. A plate containing 1536wells typically has 128 rows of 192 wells.

A variety of methods for forming a device according to the presentinvention may be used, Any method which seals the membrane within thewell of the plate (in the single plate design) and in the well of thebottom plate (in the two plate design) such that all fluid within thewell must pass through the filter before leaving the well through thebottom opening will be useful in this invention.

One method of forming such a device is to form a single plate of asuitable plastic as described above and use a mechanical seal betweenthe well wall and the filter. Such a device is shown in FIG. 6. In thisembodiment, there is a undercut 29 formed around the periphery of theinner wall of the well. The filter 27 is sized so as to fit within theundercut portion of the well. The filter is placed within the well asshown in FIG. 6. Optionally, as shown in the figure, a sealing gasket 30is applied on top of the filter within the undercut. This sealing gasket30 applies pressure to the filter 27 and ensures that all the fluid mustpass through the filter 27 thereby eliminating any leakage or bypass ofthe filter by the fluid. As shown, this gasket 30 may be in the form ofa preformed gasket such as an O-ring. Alternatively, a gasket formed ofa molten or liquid material may be cast into the undercut to seal thefilter in place. An example of a molten material suitable for thisembodiment, are any of the well-known hot melt materials such aspolyethylene or polypropylene or ethylene vinyl acetate copolymers. Aliquid gasket may be formed of any curable rubber or polymer such as anepoxy, urethane or synthetic rubber.

Another method of forming such a device is to use an adhesive to bondand seal the edge of the filter within the well such as all fluid mustpass through the filter before entering the opening in the bottom of thewell. Adhesive may be either molten or curable as discussed above.

A further method is to use a thermal bond to secure the filter to thewell. In this embodiment, a filter sealing device which has a sealingsurface which is heated is brought into contact with the upper filtersurface and transfer its thermal energy to the surrounding filter andwell material. The energy causes either the filter material or the wellmaterials or both to soften and or melt and fuse together forming anintegral, fluid tight seal. This process may be used when either thefilter material or the well material or both are formed of athermoplastic material. It is preferred that the well as well as atleast a portion of the filter material adjacent the downstream side ofthe filter be formed of a thermoplastic material. The sealing surface isonly a portion of the filter surface and is a continuous structure sothat a ring or peripheral area of the filter is sealed to the well so asto form a liquid tight seal between the filter, well and the opening inthe bottom of the well.

FIG. 7 shows one such sealing device 71 in the process of sealing afilter 72 to a portion of the well 73 such that all fluid communicationbetween the well 74 and the opening 75 in the bottom of the well 74 isthrough the filter 72. The sealing device 71, as shown has a sealingsurface 76 spaced radially outward from the center of the devicediameter and is the lowermost projection of the device. The remainder ofthe area of the sealing device lowermost face 77 is recessed in order toavoid contact with the filter 72. The sealing surface 76 is brought intocontact with the surface of a filter 72 contained within the well 74.Thermal energy is transferred from the sealing device 71 to the area offilter below the sealing surface 76. This causes either the portion ofthe filter andlor the well below that surface to absorb the thermalenergy causing it to soften or melt As the filter is porous, a portionof the filter beneath the sealing surface collapses and is renderednon-porous as well as thermally bonding to the well portion below it. Inthis manner, a fluid tight seal is formed between the membrane and thewell around the periphery of the opening in the bottom of the well.

As shown, the remainder of the face 77 of the sealing device 71 istapered inwardly as a conical depression. Altematively, the innerportion could be relatively flat leaving an outer peripheral ring asshown in FIG. 8 or any other design which accomplishes the same effect.

Additionally, the sealing surface 76 does not need to be the outermostportion of the heatsealing device 71 as is shown in FIG. 7. It may bepositioned inward from the outer edge of the device. The position is notcritical so long as an adequate seal and sufficient active filter areais maintained.

FIG. 9 shows such an embodiment. Here the sealing device 81 has theouter periphery 82 stepped inward of outer edge 83 of the device 81. Inthis embodiment, both the surface along the outer edge 83 outside thesealing periphery as well as that surface 84 inside the sealingperiphery is recessed such that only the sealing periphery contacts thefilter.

The sealing device is preferably formed of a highly thermally conductivematerial such as metal including but not limited to stainless steel,aluminum, copper or titanium. Preferably, metal/polymer heaters such assilicone faced heaters may be used. Optionally, the metal may be coatedwith a material such as PTFE resin to avoid any sticking between thedevice and the filter after sealing.

Any method may be used to heat the sealing device. Typical methodsinclude electrical resistance heaters, radiant heaters and steam orother high temperature liquid heaters which transfer their thermalenergy to the sealing device. The heaters used are not critical so longas they provide adequate thermal energy to the filter and/or well solong as a thermal bond between the filter and the well is formed.

The temperature used to create the thermal bond is dependent upon thematerials used for the filter and the well. It should be of a sufficienttemperature so as to cause a thermal softening or melting of one or theother or both of these components so that a thermal bond which forms afluid tight seal is accomplished. Preferably, the temperature selectedalso does not cause damage to either the membrane or well adjacent thearea below the sealing surface. In this way, only a select portion ofthe membrane and well are sealed to each other allowing the remainder ofthe filter inside the seal to function normally and preventing anydestruction or distortion of the well. With the types of filtersdiscussed above and the plastics typically used for making welleddevices of the type envisioned by the present invention, the temperatureof the well/filter should be in a range from about 250° F. to about 700°F. (about 121° C. to about 371° C. ). More preferably, it is in a rangeof from about 350° F. to about 600° F. (about 177° C. to about 315° C.)and most preferably from about 400° F. to about 600° F. (204 to about315° C.).

The sealing device should be designed such that it fits within the wellof the device and can be easily removed. Preferably its outer diameteris slightly smaller than that of the inner wall diameter of the well.Most wells are circular in design and the sealing device may also be ofa circular design. However, the design of the device is not so limitedso long as it fits within the well and forms a complete liquid tightseal around a portion of the filter. For example, polygonal shapes suchas triangles, squares, hexagons and other such shapes may be used.Likewise, the well design need not be circular. It too may be apolygonal shape if desired.

This is the preferred method of sealing the filter in the well of thepresent invention. It is especially preferred with ultrafiltrationmembranes. As discussed above, ultrafiltration membranes are relativelythin and fragile material and typically are cast or laminated to asupport layer to give it strength and protect its integrity. Suchmembranes are typically sensitive to heat and dryness that oftencollapse the pores of the structure rendering it non-porous. Thesemembranes usually contain one or more humectants such as one or moreglycols that prevent the membrane from drying and thus keeps the poresin the ultrafiltration membrane from collapsing. Both of theselimitations have made the sealing of an ultrafiltraton membraneextremely difficult. The humectants tend to prevent adequate sealing ofthe filter to a surface. The heat, especially in small area devices suchas multiple well plates tended to cause the collapse of a significantarea of membrane which led to a dramatic reduction in active filterarea. It has been found that this thermal bonding method will provide anadequate fluid tight seal between the membrane and the well despite theexistence of humectants such as glycols and without the collapse of theportion of the ultrafiltration membrane adjacent the seal.

EXAMPLE

A polyethylene underdrain plate of a 96 well plate known as theMultiscreen® device available from Millipore Corporation was obtained.The wells had an inner diameter of 0.300 inches. A series of filterelements formed from a cellulosic material commercially available as YMF30 membrane from Millipore Corporation were made of a diametersubstantially equal to but slightly less than the inside diameter of thewells of the underdrain (about 0.290 inches).

The filter elements were placed within the wells of the underdrain. Athermal sealing device identical of the configuration of FIG. 7, havinga sealing surface with an inner diameter of 0.235 inches and an outerdiameter of 0.265 inches made of aluminum coated with PTFE resin andbeing heated by an electrical resistance heater was inserted into eachwell with sufficient pressure to slightly compress the membrane. Thesealing device was heated to a temperature of about 460° F. for a periodof 2 seconds. The thermal energy was then ceased and the sealing deviceremoved from the well. A fluid tight seal was formed between the filterand the well surface as evidenced by a BSA test. The porosity of theremainder of the filter was also confirmed by the same BSA test.

What I claim:
 1. A filtration device comprising: an underdrain portonhaving one or more individual drain compartments, each of said one ormore compartments having an open top and a closed bottom, a drainopening formed in the closed bottom and extending through the closedbottom so as to be in fluid communication between the interior of thedrain compartment and the exterior of the drain compartment, a draincompartment wall located adjacent the outer periphery of the closedbottom; one or more filter components contained in one or more of thedrain compartments of the underdrain portion, each of said filtercomponents having a periphery of its bottom surface bonded to theunderdrain portion in a manner to form an integral seal between theperiphery of the filter component and the drain compartment of theunderdrain portion and wherein the one or more filter components areformed of a membrane selected from the group consisting of reverseosmosis membranes, nanofiltration membranes, ultrafiltration membranesand microporous membranes; and a well plate having one or moreindividual wells comprising an open top and an open bottom, said one ormore individual wells being arranged in number and location so as toregister with the drain compartments in the underdrain portion whenplaced together and said well plate being secured to the underdrainportion.
 2. The filtration device of claim 1 wherein the filtercomponent in each drain compartment is bonded at its periphery to thedrain compartment.
 3. The filtration device of claim 1 wherein thefilter components are formed of ultrafiltration membranes.
 4. Thefiltration device of claim 1 wherein all of the filter components areformed of the same membrane type.
 5. The filtration device of claim 1wherein two or more different filter components are contained within thedrain compartments.
 6. The filtration device of claim 1 wherein one ormore of the drain compartments containing a filter has two or morefilter components arranged on top of each other in each of saidcompartments.
 7. The filtration device of claim 1 wherein the filtercomponent in each drain compartment of the underdrain portion is bondedat its periphery to the drain compartment so as to form an integral sealbetween the periphery of the filter component and the drain compartment.8. The filtration device of claim 1 wherein the filter component in eachdrain compartment of the underdrain portion is bonded at its peripheryto the drain compartment so as to form integral seal between theperiphery of the filter component and the drain compartment and whereinthe method of bonding is selected from the group consisting of heatbonding, ultrasonic bonding, overmolding and solvent bonding.
 9. Thefiltration device of claim 1 wherein the filter component is bonded tothe underdrain portion by heat bonding.
 10. The filtration device ofclaim 1 wherein the filter component in each drain compartment of theunderdrain portion has at least its lowermost portion formed of amaterial having a melting point comparable to that of the underdrainportion.
 11. The filtration device of claim 1 wherein the filtercomponent in each drain compartment of the underdrain portion is formedof a ultrafiltration membrane having a highly porous support layer asits bottom layer and a ultraporous filtration layer as its upper layerand wherein the filter component is bonded to the drain compartment ofthe underdrain portion by heat bonding the periphery of the supportlayer of the membrane to the drain compartment so as to form an integralseal between the periphery of the filter component and the draincompartment.
 12. The device of claim 1 wherein the one or more filtercomponents are formed of an ultrafiltration membrane formed of a polymerselected from the group consisting of polysulphone, polyethersulphone,polyvinylidene fluoride, cellulose and combinations thereof.
 13. Thedevice of claims 1 or 12 wherein at least a portion of the well plate isformed of a light impermeable material.
 14. A multiple well devicecomprising: an underdrain portion having a plurality of individual draincompartments, said compartments having one or more drain openings, afilter support surrounding said drain opening and a drain compartmentwall located adjacent the outer periphery of the filter support; aplurality of filter components, selected from the group consisting ofreverse osmosis membranes, nanofiltration membranes, ultrafiltrationmembranes and microporous membranes, said filter components being equalin number to the number of drain compartments contained in theunderdrain porbon, each of said filter components having a periphery ofits bottom surface bonded to the underdrain portion in a manner so as toform an integral seal between the periphery of the bottom of the filtercomponent and the drain compartment of the underdrain portion; and awell plate having a plurality of individual wells, said plurality ofwells being equal in number and location with the number and location ofthe plurality of drain compartnents in the underdrain portion and saidwell plate being secured to the underdrain portion adjacent the filtercomponent.